The present invention relates to infrared sensors and in particular to an improved detector capable of detecting infrared in both the 1-3 um and 3-5 um spectral ranges.
Lead salt photoconductive sensors have been widely used in military applications since World War II. Such sensors are used for target sensing and/or tracking as well as in proximity fuses for various types of weapons. In most such applications superior results are obtained with multi-spectral detection as distinct from single spectral detection. The reason for this is that the use of two wavelengths reduces the effects of counter measures, increases accuracy, improves target detectability and decreases false alarms.
There are several techniques that are available for forming an image from scanning one or more detector arrays in the focal plane of a seeker. The high angular resolution that is necessary for target detection and tracking require that the infrared detector be disposed in a high density array. System sensitivity is increased in proportion to the square root of the number of array elements. Accordingly it is desireable to maximize the number of elements to improve sensitivity. However, since heretofore separate elements were required for the different spectral regions the number of elements in the arrays for each of the regions was necessarily half the total number of elements. Thus the sensitivity in each spectral region was heretofore reduced by attempts to increase the spectral range.
In view of the above, it is the principal object of the present invention to provide an improved infrared detector capable of detecting infrared energy within different spectral ranges.
A further object is to provide such a detector with a coincident field of view for the different spectral ranges.
A further object is to provide such a detector which differentiates infrared energy within the 1-3 um and 3-5 um spectral ranges.
A still further object is to provide such a detector which can be consistently reproduced and at a relatively modest cost.